ON THE NUDTBftANOHlATA. 



23 



steins is bifurcate, more rarely trifurcate, and each of these secondary divisions ends in 

 three (sometimes only two) small blunt points. 



Down the middle of the back runs a low distinct ridge, sending off side ridges to 

 the large branchiae but not to the small ones. There are two branchiae on each side 

 before the first of these ridges. There are four of the transverse ridges in the anterior 

 part of the body, but in the posterior portion both the longitudinal and transverse 

 ridges become obliterated. 



The veil (fig. 16) is ample, not bilobed, 9 mm. wide and projecting 2 '5 from the head 

 without the processes. It bears at each end a grooved tentacle of the shape usual in 

 Tritonia, and twelve to fourteen digitate appendages, large and small, alternating with 

 fair but not absolute regularity. The larger measure 2 mm., the smaller are about 

 half the size. 



The rhinophore sheaths are rather low (2 mm.), fairly wide, with a wavy margin. 



Via. 17. Central tooth, 

 I'rom the side. 



Kio. 18. Central tooth, 

 from above. 



Flos. 19, 20. Lateral teeth. 4 is nearer the rhacliis 

 than 5 and 6. 



FIGS. 17 to W.Tritoniopsis brucei. 



Ill front they carry two or three appendages, each bearing three points, and suggesting 

 that a branchia is fused with the sheath. The club of the rhinophore is smooth and is 

 surrounded by about twelve appendages, many of which are quite simple, while others 

 bear a few pinnae. 



The orifices are not at all conspicuous. In the specimen in which they can be seen 

 best the genital orifices lie below and between the fifth and sixth plumes, and the anus 

 between the seventh and eighth, rather higher up but some distance from the dorsal 

 margin. 



The central nervous system resembles BERGH'S figure of this organ in Atthila 

 ingolfiana (Nud. Gasteropoda of the Ingolf. Exp., pi. v. fig. 12). The four ganglia 

 are all of much the same size and round. They are mottled and apparently granulate. 

 The cerebro-pleural ganglia are not pear-shaped or larger than the pedal, and show no 

 signs of a division into two halves. The buccal ganglia are rather large. No eyes are 

 visible. 



The jaws are yellowish, fairly hard and strong, rounded, not elongate, very convex. 



(ROY. soc. EDIN. TRANS., VOL. XLI., 531.) 



